Method of cold reducing ferrous material



y 1938. J. M. SMITH METHOD OF GOLD REDUCING FERROUS MATERIAL A FiledJune 12, 1934 INVENTOR MW WWW MH w IHH Patented May 3, 1938 UNITEDSTATES PATENT OFFICE ,METHOD OF GOLD REDUCING FERROUS MATERIALApplication June 12, 1934, Serial No. 730,201

' 4 Claims.

This invention relates to the cold rolling of relatively wide strip orsheet material and more particularly to the cold rolling of ferrousmaterial in widths of and over and to tin plate and lighter gauges.

Cold rolling of sheets and strip material to such gauges is not new,even in connection with relatively wide material, but in all suchoperations, a relatively narrow range of cold reduction is employed. Forexample, it is old to produce cold rolled strip in widths of 20 andover, and in gauges as light as .0075" from stock ap proximately .060thick, and it is also old to produce such cold rolled material in gaugesfrom- .03" to .05" from stock approximating .080" to .109" thick, butmaterially larger ranges of cold reduction have not been practicedcommercially. The necessity for employing hotrolled stock of the lightergauges above noted, requires a heavy investment in hot rolling equipmentand a 'material increase in the cost of hot rolling such stock over thecost of hot rolling substantially heavier gauge stock. With this inmind, it is apparent that a material advantage is gained 'in themanufacture of sheets and sheet-like material by subjecting the materialto greater total cold reduction than has heretofore been employed incommercial operations, and I have therefore devised a method orprocedure whereby I produce strip and plate in widths of 20" or over andin gauges of .01" or less from hot rolled stock approximating inthickness.

In this connection it should be noted that the present equipment ofuniversal plate mills, now installed in the plants of many steelproducers, can, with slight additions, produce this heavier gauge hotrolled material, whereas the production of the lighter gauges of hotrolled stock involves theuse of elaborate and expensive continuous millequipment.

An object of my invention is, therefore, to produce amethod of rollingrelatively wide sheets or sheet-like material which is less expensivefrom an investment standpoint.

In all rolling operations and particularly in strip rolling operations,various expedients have been employed for the purpose of accomplishingthe desired reduction in each pass and also for the purpose of causingthe material processed, to

properly track through the pass, but nevertheless, diilicultiesencountered in connection with; the

cold rolling of ferrous material in the form of relatively wide stripand to gauges such as are here contemplated, have, as above stated,minimized thedegree of coin rolling reductions employed in commercialoperations.

A further object of my-invention is the production of a cold rollingprocedure wherein a large cold reduction such as here contemplated, isaccomplished in a single stand of rolls, and by relatively few passesthrough that stand.

The improved procedure, constituting my invention, not only results in agreater cold reduction than has heretofore been commerciallyaccomplished in connection with relatively Wide material, but it alsomakes it possible to take substantial reductions per pass andthusminimize the amount of labor and the time necessary to complete theproduct. i

I have discovered .that such cold reductions, as are here contemplated,can be obtained if it is borne in mind. thatevery portion of the crosssection of each piece cold rolled must be reduced or elongated insubstantially the same proportion. There is some indication that thishas been recognized in a vague .way,as is evidenced by the fact that thenecessity for pass control has been commented on both in patents and intrade literature. I have, however, found that in order 25 to obtain theresults here contemplated, something more than the so called passcontrol must be accomplished and while my procedure involves the use ofat least some of the old and well known expedients,'it i'nvolves anaccurate pass adjustment and such as will insure substantially equalreduction or elongation of all transverse portions of the piece or striptraversing the pass. My invention also contemplates a novel procedure inthe manner of employing these old expedients and as a result! ain ableto accomplish what has not heretofore been accomplished in commercialoperations, namely, the cold rolling of .wide ferrou's material, 20" ormore in width, to gauges such as .01 and lighter from hot' rolled stockof approximately 4" in thickness and all in a single stand of rollswithout the necessity of intermediate anneals and without changing orredressing the rolls during the cold rolling opera tion. 1

In carrying out the procedure here contemplated, I preferably employ afour-high mill, because of its rigid and rugged construction .and Ipreferably employ an old expedient to insure proper tracking to wit, Ipreferablydeliver the material to and discharge it from the mill whilemaintaining it under tension. I necessarily employ the screw-downs ofthe mill for subjecting the material tothe desired pressure for eachpass and I necessarily carefully adjust 'the screwdowns on each end ofthe mill so as to insure, as far as is possible with such adjustments,that each edge of the material or strip traversing the,

pass is subjected to the same rolling pressure.

In cold reducing the thicker stock, such as here contemplated, the firstpasses will naturally be run at less screw pressures than later passes,since the thick material permits the rolls to bite in so readily thatpractical reductions will not result from the heavier screw pressuressuch as I employ in later passes. As the cold rolling operationprogresses, the screw pressures are increased, consequently in order tomaintain a constant ratio of reduction in all transverse parts of thepiece, under the changing condition of screw pressures encountered, thechanged deflection of the rolls must be compensated for in such a way asto maintain the required pass adjustment. In other words, Where all thepasses are accomplished in a single stand, rolls of a predeterminedcontour to suit the conditions encountered in the earlier passes wherethe lighter screw pressures are employed, must have their convexityincreased for the later or heavier screw pressure passes, and thisincrease in convexity must conform to the increasing screw pressures ofthe successive passes.

I have discovered that even where an extremely rigid and ruggedfour-high mill is employed,

.the rolls distort under the working pressures encountered, andparticularly under pressures encountered in the later passes of theprocedure here contemplated. The friction between the rolls and thematerial operated upon, the molecular displacement or the distortion ofthe piece acted upon, and the active and reactive forces in general,generate heat both in the rolls and in the material traversing therolls, with the result that the rolls tend to rise in temperature as therolling operation progresses. This mechanically generated heat hasheretofore been considered a disadvantage and a source of difficulty andit is an old expedient to employ a coolant, such as water or oil and toflood either the working rolls or both the working rolls and the backingrolls with the coolant in order to dissipate this heat. The temperatureto which the rolls are raised necessarily depends upon the rate of heatgeneration and the rate of heat dissipation, or the rate at which heatis transferred from the rolls to the coolant employed. While it has beenrecognized that the heating of. the rolls results in a change in rollcontour, and while elaborate and complicated devices and systems havebeen suggested for obviating the difficulties arising from thisvariation in contour or from roll heating, no attempt has heretoforebeen made to take advantage of the mechanically generated heat and tocontrol and employ it in such a way that the contour of the rolls of asingle stand is changed in successive passes so as to compensate for thevarying conditions encountered during such passes.

One of the features of my present invention is the utilization of themechanically generated heat as an aid to pass adjustment or, as aboveset forth, as a means for changing the contour of the rolls insuccessive passes so as to compensate for the varying conditionsencountered by rea son of the successively increasing screw pressuresemployed in the successive passes. For

this purpose I provide the roll stand with a controllable supply ofcoolant so arranged that the effect of the mechanically generated heat,in accomplishing changes in roll contour, can be controlled. Thepreferred way of accomplishing this is to provide means for deliveringtwo separate flows of liquid to the rolls so that a hot liquid may beemployed on the central portions of the rolls when necessity requiresit, and while the ends of the rolls are subjected to a flow of a coldliquid. It will, of course, be apparent that to increase the convexityof the rolls to, compensate for the increased screw pressure orincreased rolling pressure encountered in the later passes, it isnecessary to conserve at least a portion of the mechanically generatedheat in the central portion of the rolls. This may be done by decreasingthe rate of heat transfer from the central or intermediate portion ofthe rolls below that at the ends oftl'ie rolls and can be accomplishedby diminishing or checking the flow of coolant to the central portionsof the rolls, or by applying hot liquid to the central portions of theface of the rolls or to the face of the upper backing roll, but in anycase, the effect is broadly the same, i. e., the rate of heat transferor heat dissipation is reduced at the central portion below that at theends, with the result that the central portion of at least one rollresponds to the increased heat retained in that portion of the roll, andconsequently takes on a convex contour, the degree of which willcorrespond to the difference in temperature between the central portionand the ends of the roll. It will, of course, be apparent that the rateof heat transfer is greatly diminished by subjecting the particularportion of the roll to a flow of hot liquid and that therefore a nicecontrol may be ob tained by providing roll flooding means so ar rangedthat the entire roll may be flooded from end to end by a cold liquid, orthe ends only of the roll be flooded by such liquid, or the ends beflooded by a cold liquid while the central portion of the roll isflooded by a heated liquid. It is of course apparent that a furthercontrol of the degree of convexity obtained may be had by providingmeans for varying the temperature of the heated liquid supplied to thecentral portion of the roll.

In carrying out my invention I prefer to so form or dress the rolls thatthey are slightly convex. During the first pass and possibly the firstfew passes, I flood the rolls with a cold liquid and in such quantitiesas to insure a rate of heat transfer from the rolls to the liquid aswill maintain the rolls cold and thus insure maintaining thepredetermined contour during the rolling operation. In the later passes,I flow cold liquid in adequate quantities over the ends of the rolls tokeep the ends cool and to dissipate the mechanically generated heat fromthose portions of the rolls, but at the same time proceed so as to buildup the temperature of the central portion of at least one of the rolls.That is, I'may reduce or check the quantity of cold liquid delivered tothe central portions of the rolls, and I may flood the central portionsof the rolls with a hot liquid while maintaining the flow of cold liquidover the ends of the rolls. This last mentioned procedure is resorted toin the last few passes, or when the metal being processed is of-lightgauge and the rolling pressures are high, but in all cases I obtain thepass adjustment here contemplated by maintaining a temperaturedifferential between the ends and the center of at least one of thebacking rolls and in progressively increasing this differential toeffect a progressive increase in the convexity of such roll tocompensate for the rolling pressures encountered.

ile I have generally outlined the preferred procedure for takingadvantage of, and efiectively utilizing the mechanically generated heat,it will be apparent that a substantial reversal of the procedure hereoutlined may be resorted to. That is to say, the mechanically generatedheat .may be utilized to increase the temperature of the roll or rollsduring the earlier passes and the pass adjustment, essential in thelater passes, may then be obtained by flooding the ends of one or moreof the rolls in such a way as to control the rate of heat transfer fromthose portions of the roll or rolls, while maintaining the temperatureof the central portion of the roll or rolls.

The entire pass adjustment is for the purpose of issuing substantiallyequal reduction or elongation of each transverse portion of the piece orstrip simultaneously traversing the rolls, since it y will be apparentthat if the contour of the rolls is not adjusted to compensate for thedeflection occasioned in the rolls by the various screw pressuresencountered, the edge of the piece or strip will be over-rolled,resulting in a pinching or tearing of the strip, or the central portionof the piece or strip will be over-rolled, resulting at the best in anobjectionable product.

My invention may be summed up as a coldrolling procedure employed inconnection with a single stand of rolls, wherein that stand is employedin reducing strip material by successive passes and wherein a passadjustment is resorted to which compensates for varying pressuresencountered in the different passes and insures substantiallyequalreduction or elongation of every transverse portion of the piece orstrip simultaneously acted upon by the rolls. This enables me toincrease the total cold rolling reduction above such as has beenheretofore employed in commercial operation, and it therefore enables meto employ a cheaper andmoreeasily obtained hot rolled stock, as comparedto the lighter gauge material. This heavy stock may be obtained, in manycases, from existing rolling mill equipment, whereas the light gaugematerial must be produced on an expensive continuous mill or itsequivalent.

In the accompanying drawing, Figure l is a diagrammatic side elevationof apparatus, such as may be employed in carrying out my invention; and

Fig. 2 is an end elevation of a four-high stand of rolls such as isillustrated in Fig. l.

In order to more'fully disclose the procedure involved by my invention,I refer particularly to the apparatus disclosed by the drawing, but onlyfor illustration purposes. The apparatus consists essentially of afour-high mill 3, reels of coilers l, 4', and idler or guide rollers 5,5. The mill 3 includes working rolls 6, 6' and large diameter backingrolls 1, i.

All these rolls are mounted in the usual way in a housing 8 and thehousing is provided with the usual screw-downs 9, one of which islocated at the top of each housing and which are employed for varyingthe setting of the rolls 6, 6' or for the purpose of varying the rollingpressure to which the piece is subjected during the cold rollingoperation here contemplated. Any suitable means may be employed fordelivering flooding liquid to the rolls, provided such means is capableof controlling the flow of such liquid in the manner heretoforedescribed.

In the drawing I have illustrated three sets of sion as the rollingoperation progresses.

nozzles it, ill and if, so located and arranged that the outermostnozzles Ilil are adapted .to

deliver a flooding flow of liquid to the ends of the working face of theupper backing roll i, whereas the nozzles ii. are adapted to deliversuch a flow to the intermediate portion of the working face of thatbacking roll. A liquid delivery pipe We is shown communicating with oneset of nozzles. Wipers it may be employed for the purpose of,

to some extent, confining the flow of liquid dem livered by the variousnozzles and the arrangement of the wipers may besuch as to in effectprovide three compartments, each opening onto the face of the associatedbacking roll and each provided with a drain pipe it. For example, the warrangement may be such as to provide compartments it, M, in which thenozzles [It-it are located, and a central compartment it in which thenozzles ii function.

Such an arrangement of compartments insures the roll. It will, however,be apparent that details of constructionof the mechanisms employed fordelivering the flooding liquid to the roll or rolls is not essential solong as the arrangement is such that the flooding mechanisms are capableof delivering sufficient liquid to insure a high 0 rate of heattransfer, and thus maintain all portions of the rolls cold when it isdesirable so to do. In carrying out my invention, I place a coil of hotrolled stock W in a decoiling box H, which is associated with a seriesof pinch'and flattening g5 rolls ill and H8. The forward end of thestock is passed through the rolls Ill and it, over a guide roller IS, aconveyor 20 and the guide rollers 5 and into and through the passdeflned by the reducing rolls 6i5. This forward end is 40 then passedover the guide roller 5 and secured to the coller 4', on which it iswound under ten- The stock on .the entering side of the stand is notunder tension during this, its first pass, through 5 the mill. Thisstock is approximately A" thick and of the desired width and. length.

When the rear end of the stock approaches the rolls 6-6 of the stand,the mill is reversed and this rear end is fed into and attached to thecoller d, which is then so driven that the piece being rolled is undertension during the second pass of the material through the mill. It willbe understood that the caller 4 is so operated,.dur

ing this pass, as to impose tension on the strip 5 as it enters themill, and I prefer to so gauge the tensions on the entering and exitside of the mill that the stress in the material occasioned thereby issubstantially equal on both sides of the mill.

It should be understood that this tension does not so exceed the elasticlimit ofthe material, either on the entering or leaving side of themill, and that the pull exerted by the coller 4"is preferably such thatthe drag of the strip on the entering side is greater than the pull ofthe strip on the exit 05 side. After the second pass is completed, thedirection of rolling is again reversed and the piece is then subjectedto the desired number of back and forth passes through the mill, withboth ends continuously secured to their respective coilers andmaintained under approximately equal tension, as above described, anduntil the predetermined gauge is reached. A

It will, of course, be understood thatif the coil or hot rolled stock ison a spool, the spool Cal may be mounted in the position indicated byeither coiler 4 or 4. The end of the hot rolled stock is then guidedover the associated roller 5 or 5' and into and through the pass definedby the working rolls 66, whence the process as above described isfollowed, except that the rear end of the stock is already secured toone of the coilers 4-4 and consequently the first pass may beaccomplished while both the entering and exit portions of the materialare maintained under tension.

Thus the strip stock passes first in one direction and then in the otherthrough the mill and each pass accomplishes a material reduction on thestrip. I contemplate reducing the hot rolled stock to final gauge by aminimum number of passes and, for this reason, I contemplate asubstantial reduction per pass. The following table discloses examplesof actual commercial practice and sets forth the procedure herecontemplated in terms of number of passes, the gauge of material as itenters and leaves each pass, and the percentage of reduction per passand the pressure, in thousands of pounds on the neck of each backing uproll.

A reference to the table discloses that the pressures are graduallyincreased from 900,000 pounds to 1,300,000 pounds. In this example ofthe rolling procedure, nine passes were employed for reducing hot rolledstock having a thickness of .265 inch to the finished product having athickness of .0088 inch, and one of the features of the invention is toaccomplish the cold rolling reduction in a minimum number of passes, i.e., from 7 to 9, or even fewer passes. It will be apparent that thetable is merely illustrative of the procedure here disclosed and thatthe rolling pressures will naturally vary with the varying Width andthickness of the material rolled and as the reductions and number ofpasses are modified.

In carrying out the procedure as exemplified by the table, the workingrolls 66' are preliminarily dressed so that each has a convexity ofapproximately ,006" in diameter. During the first passes a sufiicientfiow of coolant is de livered to all portions of the rolls to maintainall portions of the rolls cold. The strip traversing the pass is alsoflooded with sufficient cooling liquid to keep it cool. Throughout theentire procedure, as defined, I flood at least the end portions of therolls with sufficient cooling liquid to maintain them reasonably cold.As the rolling pressures increase throughout the successive passes, Imanipulate the flow of liquid to the rolls and the temperature of theliquid in sucha way as to establish what may be termed a thermal crownon at least one of the rolls. That is to say, I so manipulate theflooding liquid as to maintain the pass adjustment heretofore referredto, and'this may be accomplished by building up a thermal crown, of theright degree of convexity to maintain the pass adjustment, on onebacking roll only.

There is some advantage gained by limiting the thermal crown to onebacking roll, since in so doing, I accomplish the pass adjustment, frompass to pass, by larger variations in the thermal crown than wouldbepossible if a thermal crown were built up on both backing rolls 1-1 oron both reducing rolls 66 and in this way, I halve such error as theoperator may make in building up the crown and therefore minimize theeffect of the error, with the result that the commercial operations arespeeded up by reason of the fact that the pass adjustment is renderedless sensitive.

It will be apparent, from what has been said, that this pass adjustmentmay be accomplished. throughout the successive passes, by reducing theflow of cooling liquid to the central portion of the face of one backingroll, by checking the flow of this liquid altogether, and by deliveringa heated liquid to that portion of the face of the backing roll, and inthe drawing, I have diagrammatically illustrated apparatus for thuscontrolling the flow of flooding liquid to the upper backing roll. Itwill be apparent that the preferred procedure contemplates an adequateflow of cooling liquid over the end portions of the face of the upperbacking roll at all times for the purpose of dissipating themechanically generated heat in those portions of that roll.

In carrying out the defined procedure it is desirable to keep the endsof the rolls as cool as possible, in order to accentuate the effect ofthe mechanically generated heat and to obtain a greater variation in thedegree of roll convexity in accomplishing the pass adjustment herecontemplated, and that therefore provision should be made for anadequate and copious flow of coolant.

By following the procedure above outlined, each pass can be so adjustedas to compensate for the effect of roll deflection encountered duringthe pass. It will also be apparent that some advantage and someflexibility of control may be gained by employing heated liquids ofdifferent temperatures, although satisfactory results have been obtainedby employing hot oil at a temperature approximating 190 F., sinceconsiderable flexibility is obtained by varying the rate of flow of thehot oil to the central portion of the face of the uppermost backingroll.

While I have set forth what I now consider to be the preferred procedurein cold rolling hot rolled stock from approximately A" in thickness tothe lighter gauges of commercial sheets, and black plate, it will beapparent that various changes in the procedure may be resorted towithout departing from the spirit and scope of the invention, whichresides primarily in maintaining a'pass adjustment, during thesuccessive passes of the material through the mill, such that alltransverse portions of the strip, simultaneously acted on by the rolls,are reduced or elongated substantially equal amounts.

What I claim is:

1. A method of cold rolling hot rolled ferrous stock in the form ofrelatively wide strip approximately one fourth inch in thickness to thegauges of commercial strip, which consists in passing such stock backand-forth through a single fourhigh stand of rolls, in increasing therolling pressure exerted on such material in its passage through therolls and as its thickness is reduced,

in maintaining a temperature differential between the ends and center ofat least one of the backing' rolls of such stand and in increasing suchdifferential to compensate for the increased deflection in the rolls ofthe stand occasioned by such increased rolling pressure.

2. Amethod of cold rolling strip material which includes subjecting ahot rolled work piece of fer- -rous metal having, a thickness of atleast three .sixteenths of an inch to successive cold reduc- 3, A methodof cold reducing ferrous stock in the form of relatively wide strip ofapproximately one fourth inch in thickness to the lighter gauges ofcommercial sheets, whichconsists in passing such material back and forththrough a single four-high roll stand, in increasing the rollingpressure exerted on such material in at least the later passes, inmaintaining a temperature differential between the ends and center of atleast one of the backing rolls and in varying such differential tosubstantially compensate for the increased deflection in the rollsoccasioned by the increase in roll pressure.

4. A method of cold rolling strip material, which includes subjecting awork piece to successive reductions in a single four-high stand ofrolls, in increasing the rolling pressure in at least the later passes,in maintaining a temperature differential between different portions ofat least one of the backing rolls and in increasing such temperaturedifferential to substantially compensate for the increased deflection inthe rolls oc-' casioned by such increase in rolling pressure.

jJAME S menu-m.

